You have tried albendazole with no killing evident.
If the invermectin (IVM) challenge test is negative, consider the phylum of the
parasite is not a roundworm that has a filarial stage (the popular bad boys). Keep in mind that IVM does not stop the wiggles, or adult worms, but stops the small, toxic, babies. GERD or Acid reflux is typical reaction to
Ascaris or Strongyloides that come from the lungs. About 60% of the folks have a challenge response, although many see the challenge not work in subsequent challenges, and over time, the response is less and less.
Adults can be stopped using different meds, I believe only dead end
parasites have no babies.
It is possible you have a dead end parasite, or you are being infected by a (source) series of infections by a source of dead end (do not multiply in a human) parasites.
Other Choices.
This leaves quite a few species and phylums. I assume you verified the IVM dose level twice. Reaction in two hours is typical, with suppression of the filarial stages for 18 hours.
So far, I have messaged with people with screw worms, pinworms, unidentified filarial worms, Ascarids, Strongyloides, and many others. I have heard of bad pinworm infections, but never corresponded with anyone that has this
parasite disseminated head to toe. There would have been blood in the stool. Same for bad hook worm infections.
Occasionally (30% of the time) people present with severe fluke infections, but these people nearly all have a second
parasite infection, typically filarial. Flukes cause electrical zaps in the back of the head/brain.
What period of time did the infection present over?
You may want to consult a tropical disease doctor. There are only a few around that practice. They may want to try to retrieve a sample for a pathology report.
Roundworms are usually not localized to an area, and do not start in the head and move down. They start in the gut, lung, feet. Loa Loa and other water based worms can start in the eye, but most respond to albendazole or invermectin.
Given the location, and knowing the infection is not loa loa, I would consider the parasite is a completely different family.
If all else fails, I can explain the latest types, dose levels, and things that work the best that I am familiar with.
The PinX dose test says have a macro zoom camera ready to see if
parasites come out in the stool. About 2/3 people are challenged by PinX since it is broad spectrum, and most parasite species have at least one stage that relies on the GI tract.
Some people have gone all the way to the Praziquantel challenge test before showing parasites, but this is running about 1/40 people.
There are marine phylums that respond to praziquantel, but some do not.